Sustainablility of Hydrogen Fuel Cells

Sustainablility of Hydrogen Fuel Cells

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Description: Prospects of Fuel Cells and Hydrogen, Sustainable Energy Systems, Hydrogen like electricity is an energy, Fuel cells for transportation, Current Hydrogen Supply and Fuel Cell Utilization, Economics of Hydrogen Fueling Scenarios, Sustainable Paths to Hydrogen, Renewable Hydrogen Supply, Fuel Cell Technologies.

 
Author: Greg Jackson (Fellow) | Visits: 1807 | Page Views: 2393
Domain:  Green Tech Category: Battery & Fuel Cell Subcategory: Hydrogen Fuel Cells 
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Link Back: Woodrow Wilson International Center for Scholars
Short URL: https://www.wesrch.com/energy/pdfTR1YL6EJRJLHY
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Contents:
Prospects of Fuel Cells and Hydrogen:
"Seeing Beyond the Press Releases"
Prof. Greg Jackson Chair of UMERC Steering Committee e-mail contact: gsjackso@eng.umd.edu

University of Maryland, College Park, USA

Sustainable Energy Systems:
Energy systems that can last for millennia (adapted from John Turner, NREL 2006) Questions for the Future of Energy: � Sustainability � Resource availability � Energy Payback � Environmental impacts � Geopolitical factors � Security � Supply for emerging markets � Providing a sustainable energy carrier for transportation Answers: � Biomass � Solar � Wind � Geothermal � Nuclear � Hydrodynamic � Wave � Hydrogen

University of Maryland, College Park, USA

Why Hydrogen?
� Hydrogen like electricity is an energy carrier not an energy supply
� Unlike electricity, it can be stored relatively easily � Unlike hydrocarbons, it does not necessarily lead to local CO2 and other emissions



Fuel cells for transportation will dictate the needs for H2 infrastructure
� Leaders: Ballard, GM, Honda, UTC, other auto manufacturers � Low temperature fuel cells currently requiring high purity H2 ( 5000 hrs.) � Hydrogen IC engine as an alternative (BMW and Ford investing in this)



Hydrogen is clean and can be produced from several sources
� Fossil fuels with easier CO2 sequestration � Low-temperature electrolysis � Nuclear power with high temperature electrolysis or thermochemical cycle



Current Use of Hydrogen: ~ 9 million tons/yr in U.S. and growing
� Equivalent in energy to about 0.3% of annual U.S. oil consumption � > 90% of H2 production comes from steam reforming of natural gas ( CH4 + H2O ) � Primary uses today: are for refining petroleum and producing ammonia

University of Maryland, College Park, USA

Current Hydrogen Supply and Fuel Cell Utilization
� Approach for today involves reforming natural gas to H2 and CO2 � Overall well-to-wheel efficiencies are comparable to current-day hybrid vehicles but can be surpassed by proposed diesel hybrids (Wang 2003) � Green-house gas emissions lower than proposed hybrids, but limited NG supply raises questions of sustainability (Wang 2003)

NG Fuel Supply
CO2 Exhaust

We ll t o

Ta

adapted from S. Limaye (2004) for Oak Ridge Nat. Lab

nk Ta nk to W

Fuel Processor
?H

Air

Combustor

Hydrogen Clean-Up

< 5 ppm CO

he el

Waste CO, CO2, other pollutants

Hydrogen Storage

H2O Exhaust

Fuel Cell
University of Maryland, College Park, USA

Economics of Hydrogen Fueling Scenarios
Gasoline Marketers Association: $2 billion to convert 10% of current retail stations to hydrogen. Shell Hydrogen: $19B for 25% conversion
Alternative Local Production: Home Refueling

University of Maryland, College Park, USA

Sustainable Paths to Hydrogen
from John Turner, NREL 2006 Solar Energy Solar Energy

Heat Heat

Biomass Biomass

Mechanical Energy Mechanical Energy

Electricity Electricity

Conversion Conversion

Thermolysis Thermolysis

Electrolysis Electrolysis

Photolysis Photolysis

Hydrogen Hydrogen
University of Maryland, College Park, USA

Renewable Hydrogen Supply
adapted from John Turner, NREL 2006
� Renewable approaches to hydrogen supply still face challenges. � Low efficiency of electrolyzer � Need for large-scale storage if non-local production
ePower Electronics Electrolyzer

H2 O2

Gaseous Hydrogen Transmission Pipeline Gaseous Hydrogen Fuel Market Energy Storage in Pipeline

Wind Generators

H2O

ePower Electronics Electrolyzer

H2 O2

Gaseous Hydrogen Geologic Storage ???

H2O

GW-hrs of energy storage are necessary if large scale generators are needed

Solar Generators

Oxygen Sales to Nearby Gasification Plants

Bill Leighty, http://www.leightyfoundation.org/earth.php University

of Maryland, College Park, USA

Fuel Cell Technologies Going Forward
� Proton Exchange Membrane Fuel Cells � Solid Oxide Fuel Cells
� Operation at low temperatures < 120�C � Expensive precious metal catalysts � Fuel limited to relatively pure H2 with inerts for high power applications � For portable power, dilute methanol or ethanol mixtures may become viable � H2O management critical for most designs � Operation at high temperatures > 600�C � Inexpensive catalysts � Potential for fuel flexibility � coal gas, NG, ethanol, biomass gases � Ideal for integration with C sequestration � Readily integrated with gas turbines for high efficiency hybrid plants

� SOFC primary applications � � PEMFC primary applications � vehicles, small gensets, portable power stationary / distributed power, APU's

85 kW H2-fueled automobile PEM fuel cell stack provided by Ballard Power Systems

SOFC single cell schematic provided by R.J. Kee, Colorado School of Mines

University of Maryland, College Park, USA

PEM Fuel Cells �Challenges and Breakthroughs
� Vehicular fuel cell system development has brought this technology to some maturity but costs remain high even for mass production ($75 - $100/kW) � Current DOE plan to make commercialization decisions regarding transportation fuel cells and large-scale H2 production by 2015. � Markets with high kW costs provide best opportunities for today � Electronic devices, portable generation, utility transport, public transport � What are the barriers � Cost (precious metal catalyst and expensive polymer membrane) � Storing pure H2 supply � Systems issues (H2O management, storing pure H2 or processing fuel) � What are forward looking solutions � Electrocatalyst with less precious metals � Higher temperature polymer membranes � More efficient H2 purification processes � Light and safe materials for H2 storage University of Maryland, College Park, USA
Fuel Cell System Cost (2000-2010) From Ballard Power Systems

SOFC's � Identifying Technical Challenges and Breakthroughs
� Stationary power SOFC development funded by DOE has led to one realization, but further funding for small-scale power has led to new technology. � Fabrication costs remain high for SOFC's (~$400/kW) � Operational cost benefits from very high efficiencies (>60% with hybrid gas turbine/SOFC's) and possible cogeneration. � Markets with high fuel costs and steady operation �military portable generation and remote distributed power � provide best opportunities � Materials issues still to be resolved for improved fuel flexibility and operability � What are the barriers � Low-temperature ceramic membranes � Low-cost catalyst with fuel flexibility and durability � What are forward looking solutions � New lower-temperature ceramic membranes � Electrocatalyst layers with fuel flexibility and durability � Improved integration with small gas turbines � Integration with sequestration technology
Cost breakout for NG-fired SOFC's TIAX Carlson et al. 2004
Cost per m2 of fuel cell membrane

University of Maryland, College Park, USA

Nano-architectured Catalysts for PEM Fuel Cells
Profs. B. Eichhorn, G. Jackson, Ballard Power Systems
� Developing nanoparticle architecture through controlled liquid synthesis to design stable catalysts that have active precious metals only on outer shell � Reduced precious metal requirement � Nano-architectures provide superior tolerance for primary H2 impurity, CO. � Successful development may improve PEM fuel cell system efficiency and operability with bio-derived fuels.
Example Au@Pt heteroaggregate particles for H2/CO oxidation
In 50%H2, 0.2%CO, 0.5%O2, Ar balance, Au@Pt nanoparticles light-off at lower T than pure Pt or Au + Pt nanoparticles for CO and H2 oxidation.
100 90 80 70 60 50 40 30 20 10 0 80

Conversion or yield (%)

Au
Au@Pt Pt

Au@Pt
Yield of H2O Yield of CO2 Conversion of O2

Pt

100

120

140 160 180 Temperature(oC)

200

220

240

University of Maryland, College Park, USA

High-Temperature Fuel-Flexible Solid Oxide Fuel Cells
Profs. G. Jackson, B. Eichhorn, R. Walker � Exploring fundamental material issues to provide new understanding for optimizing design solid oxide fuel cell assemblies for operating on hydrogen, bio-derived fuels, and fossil fuels � System design tools being developed to explore how solid oxide fuel cells can be used for making CO2 capture more feasible.
Optically accessible rigs for laser diagnostics to evaluate new materials Micro-fabricated fuel cell architectures to understand chemistry of H2 and other fuels
1.2 98% H2 2% H2O 85% H2 15% H2O 1.8 62% H2 38% H2O 1 50% H2 50% H2O 1.6 25% H2 75% H2O 1.4 0.8

Experimentally validated models for fuel cell design
2

Power Density, V i (W/cm ) Power Density, V i (W/cm ) Power Density, V i (W/cm ) Power Density, Vcelli (W/cm2)

Voltage, Vcell (V)

Vcell Ni oxidation limit
0.6

1.2 1

0.8 0.4 0.6

488 nm Ar ion & 633 He:Ne lasers (up to 25 mW at 100%) Spectral resolution of ~1 cm-1 Temporal resolution of ~1 minute

0.4

Four independent patterned Ni electrodes with common LSM/YSZ porous cathode

0.2 0.2 0 0 0

Current Density, i

2

4

(A/cm2)

6

8

University of Maryland, College Park, USA

H2 and Fuel Cells: Identifying the Opportunities
1 Exajoule = 2.77*1011 kWh
Potential for central power SOFC's with carbon capture Potential for distributed power with combined cooling and heating with SOFC's and PEMFC's Potential for H2 derived from non-petroleum sources for PEMFC powered vehicles
from Lawrence Livermore Natl. Laboratory http://eed.llnl.gov/flow (June 2004)

University of Maryland, College Park, USA

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